Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 08-16-04, 09:10 PM   #1
rj987652003
Guest
 
Bikes:
Posts: n/a
Mentioned: Post(s)
Tagged: Thread(s)
Quoted: Post(s)
61T chain ring on 1978 suntour equipped Fuji possible?

What is the largest chain ring I can put on my suntour equipped late 70's Fuji road bike? Is a 61T possible? Can I adjust the front derailler enough to compensate. Will the chain be long enough?
  Reply With Quote
Old 08-16-04, 09:28 PM   #2
sch
Senior Member
 
Join Date: May 2003
Location: Mountain Brook. AL
Bikes:
Posts: 3,008
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Yes, 61T can be fitted, the front der will have to be moved up on the seat tube
perhaps an inch or so. The small chainwheel shift will be clumsy at best and a
triple front der would be a good idea because of the longer cage. Ditto long cage
rear der to wrap chain. Chain will definitely be short, but if you keep the chain on
the outer 4 cassette cogs it would work (Cogs less than 20-21T). Really should
add 4-5" of chain though to prevent inadvertent disaster. Use of a 61T with
650 or larger wheels doesn't make much sense though. A 61x13 with a cadence of
100rpm would be ~37mph. Recumbents with their tiny wheels routinely use triples
with 60-62T x 42 x 26 or 24 combos and shift ok. But they dont have to worry
about chain line or chain wrap as much. Steve
sch is offline   Reply With Quote
Old 08-16-04, 09:46 PM   #3
rj987652003
Guest
 
Bikes:
Posts: n/a
Mentioned: Post(s)
Tagged: Thread(s)
Quoted: Post(s)
Thanks for the good technical advice. Do you think I could get away with a 56 without switching deraillers? Am I going to have to use a custom chain or is there an off the shelf chain that can work?
  Reply With Quote
Old 08-17-04, 06:39 AM   #4
dafydd
JRA...
 
Join Date: Oct 2003
Location: philly
Bikes: trek 520 & 736, DeRosa Professional, Fuji Professional, Raleigh International 3-speed, Saronni (any info people?), Humber 3-speed, Raleigh Sports, Carlton Grand Prix coming soon!
Posts: 839
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Sure, you can probably do it... provided you have a crankset for which a 61T chainring is available.
dafydd is offline   Reply With Quote
Old 08-17-04, 07:56 AM   #5
Gonzo Bob
cycles per second
 
Gonzo Bob's Avatar
 
Join Date: Oct 2003
Location: Minnesota
Bikes: Vitus Aluminum, DiamondBack Apex, Softride Powerwing 700, "Generic" Ishiwata 022, Trek OCLV 110
Posts: 1,790
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
road front derailers are typically designed for a big ring between 50 and 56. You can go bigger than that, but the curvature of the derailer cage will be tighter than the chain ring. This means you will have a bigger gap between cage and ring at the front of the cage than at the back - i.e. you won't be able to get the derailer as low as you would like for best shifting performance. It will still work, though. Most front derailers for double chainring typically are spec'd at a max difference of 15 or 16 teeth. A late '70s Fuji probably has a Sugino crank with 144mm BCD and 42x52 chainrings. So changing to 42x61 would give you a difference of 19 teeth. It will still work, but you have to be careful not to run the small-small combos or the chain might drag across the bottom of the derailer cage.

I recommend getting a new chain if you do it. Any 6/7/8-speed chain will work.
Gonzo Bob is offline   Reply With Quote
Old 08-17-04, 08:49 AM   #6
sch
Senior Member
 
Join Date: May 2003
Location: Mountain Brook. AL
Bikes:
Posts: 3,008
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Most off the shelf chains are 3-4" too long as supplied. You could start with a new
chain and splice in another 1-2". The LBS may have a few spare links floating
around, as chains are almost always shortened when installed. That assumes there
will be no incompatibility with the new chain and older cassette from wear. 5-7spd
chains are dirt cheap, perhaps $8-15 range. 56T CW would reduce the stress on
the system significantly but the chain would still need to be a bit longer, the rear
derailler may be able to wrap without going to a longer cage. Steve
sch is offline   Reply With Quote
Old 08-17-04, 09:18 AM   #7
RainmanP
Mr. Cellophane
 
RainmanP's Avatar
 
Join Date: Nov 2000
Location: New Orleans, LA
Bikes:
Posts: 3,037
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Why would you waste mental energy on something like this? Are you actually overspinning your 52/11?

Added later: Sorry, after reading that I realize it sounded smartass, which was not my intent. But do you really need a 61?
__________________
If it ain't broke, mess with it anyway!
RainmanP is offline   Reply With Quote
Old 08-17-04, 09:25 AM   #8
Phatman
Senior Member
 
Join Date: Sep 2002
Location: NC
Bikes:
Posts: 3,411
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I was gonna say that myself, rainman. I think we have another merton on our hands
Phatman is offline   Reply With Quote
Old 08-17-04, 10:46 AM   #9
supcom
You need a new bike
 
supcom's Avatar
 
Join Date: Aug 2002
Bikes:
Posts: 5,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I think he's trying to make up for having a 14t smallest sprocket on the freewheel to get similar to 52/11 gear ratio.
supcom is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 01:27 PM.